European patent application No. 37,092 describes compounds endowed with a high acaricide activity, among which also the compound 1-decyloxy-4-[(7-oxa-4-octynyl)-oxy]-benzene of formula: ##STR1## (hereinafter referred to as compound I).
In the abovesaid European patent application there are described also synthesis processes suitable for preparing the different acaricide compounds.
These processes include also the process indicated in the following scheme 1, where it is described in the specific form suitable for the synthesis of compound I. ##STR2##
Reaction 1 of Scheme 1 consists in protecting the alcoholic function of 3-bromo-propanol in order to prepare the successive reaction.
Reaction 1 is illustrative of the preparation of the tetrahydropyranyl derivative, but it is possible to protect the hydroxy group also according to other variants known in organic chemistry.
Reaction 2 represents the reaction between the lithium salt (acetylide) of methyl-propargyl-ether and the 3-bromo-propanol protected on the alcoholic functional group (A).
Acetylide is generally prepared in situ by reacting methyl-propargyl-ether with lithium-butyl.
Then it is necessary to free the product obtained by reaction 2 (B) from the protective group on the terminal hydroxy group (reaction 3). The resulting alcohol (C) is then converted into the corresponding p.toluene-sulphonic ester by reaction with p.toluene-sulphonic acid chloride in order to transform the terminal hydroxyl group into a group more reactive as "leaving group" (reaction 4).
p.toluene-sulphonate (D) is then condensed with the sodium salt of 4-decyloxy-phenol according to reaction 5.
The process described hereinabove exhibits several drawbacks which reduce its validity from an industrial viewpoint. These drawbacks depend on the necessity of carrying out necessary but expensive operations, such as the protection of the hydroxy group (reaction 1), removal of the protective group from hydroxy group (reaction 3) and functionalizing the hydroxy group as p.toluene-sulphonate (reaction 4).
These and other reactions require the use of expensive and dangerous reagents such as lithium-butyl and p.toluene-sulphonic acid chloride, which are practically impossible to recover.
Furthermore, in connection with the fact that the process comprises a number of steps and that for some of such steps it is necessary to isolate the intermediates obtained, the process yields are not particularly high.